linux-kernel - Re: [PATCH] acpi memory hotplug, add parameter to disable memory hotplug for kexec

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Date:	Fri, 10 Jan 2014 06:01:26 -0500
From:	Prarit Bhargava <prarit@...hat.com>
To:	Yasuaki Ishimatsu <isimatu.yasuaki@...fujitsu.com>
CC:	Vivek Goyal <vgoyal@...hat.com>,
	KOSAKI Motohiro <kosaki.motohiro@...il.com>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	linux-acpi@...r.kernel.org, Len Brown <lenb@...nel.org>,
	linux kernel mailing list <linux-kernel@...r.kernel.org>,
	Dave Young <dyoung@...hat.com>,
	Kexec Mailing List <kexec@...ts.infradead.org>
Subject: Re: [PATCH] acpi memory hotplug, add parameter to disable memory
 hotplug for kexec



On 01/09/2014 10:57 PM, Yasuaki Ishimatsu wrote:
> (2014/01/10 6:44), Vivek Goyal wrote:
>> On Thu, Jan 09, 2014 at 04:34:16PM -0500, KOSAKI Motohiro wrote:
>>> On Thu, Jan 9, 2014 at 10:00 AM, Vivek Goyal <vgoyal@...hat.com> wrote:
>>>> On Thu, Jan 09, 2014 at 12:00:29AM +0100, Rafael J. Wysocki wrote:
>>>>
>>>> [..]
>>>>>> The system then panics and the kdump/kexec kernel boots.  During this boot
>>>>>> ACPi is initialized and the kernel (as can be seen above)
>>>>>
>>>>> Which is a bug.  You're not supposed to initialize ACPI twice in a row.
>>>>
>>>> [CC lkml, kexec mailing list, dave young]
>>>>
>>>> It is a fresh instance of kernel booting and it is initializing its data
>>>> structures fresh. It is *not* re-initializing ACPI in same kernel.
>>>>
>>>>>> This patchset resolves the problem by adding a kernel parameter,
>>>>>> no_memory_hotplug, to disable ACPI memory hotplug.  It can be added by
>>>>>> default
>>>>>> as a parameter to the kexec/kdump kernel so the kernel boots correctly.
>>>>>
>>>>> This problem is specific to kexec/kdump, so please don't add *generic* command
>>>>> line parameters to address this.
>>>>>
>>>>
>>>> There are other command line options to solve kdump problems. In general
>>>> one might want to disable memory hogplug on the fly even if it is compiled
>>>> in the kernel. So it can act as a good debugging aid.
>>>>
>>>> Secondly, it can be specified with memmap=exactmap and mem=X paramters to
>>>> make sure no memory is hot added in the system.
>>>>
>>>> So I can see other usages of this parameter. To me it makes sense to have
>>>> a separate command line option to disable memory hotplug feature on the
>>>> fly.
>>>
>>> I'm ok this option. But note, even if this option is specified, SH,
>>> Power and S390 still
>>> be able to use memory hotplug because their firmware are totally
>>> different from ACPI.
>>>
>>> Maybe, adding acpi prefix provides good clarification.
>>
> 
>> Makes sense. Something like "acpi_no_memhotplug" or "acpi_disable_memhotplug"
>> or something else.
> 
> I like Prarit's patch and the boot option name. If it is updated,
> I'll test it.

I'm going with "acpi_no_memhotplug" and I'm testing across several systems right
now.  Will send out a new patch shortly.

P.

> 
> Thanks,
> Yasuaki Ishimatsu
> 
>>
>> Thanks
>> Vivek
>>
>> -- 
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> 
> 
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